What's good: With so many music apps in the AppStore, you wouldn't expect there to be too much innovation when it comes to that particular category. Titles like Tap Tap Revenge, Guitar Hero, and (recently) Thumpies seem to have developed on most of what there is to a good rhythm game, and to that end, countless game studios have tried to imitate these originals.

As the biggest and most successful music company in the world, Universal Music Recordings naturally upholds a certain standard, and while at first you might think their newly released app Six-String simply copies off others' ideas, you'll think differently once you play the game.

Simply put, Six-String combines some of the most realistic guitar mechanics we've ever seen on a mobile device with fun and challenging gameplay.The rules are simple enough - anticipate as color-coded notes move towards the guitar's pickup (these are coils located on the Tailpiece near the bottom of the instrument) and tap, swipe, or hold appropriately as soon as the cues cross directly overhead. Pluck virtual strings when you see green dots, hold until the end of yellow lines, and strum your finger(s) across blue or green arrows. Medium and difficult levels will require you to occasionally change chords as well, and to do this, simply tap on the blue button that appears at the bottom of the screen. If you're too early or too late at any point of the game, the resultant music will sound a little off, and you'll lose any streaks you were building as well as decrease your accuracy percentage. On the other hand, hitting notes perfectly will increase both a health and a multiplier meter that (when full) lets you shake your device to multiply points by eight for a short period of time. Your level, progress, scores, track variety, and game sessions contribute to something called the 'Shred Cred' as well as a 'Hall of Fame' score.

There are several licensed music tracks that come with the app, including Bon Jovi's "You Give Love A Bad Name," Orianthi's "According To You," and Fall Out Boy's "Thnks Fr Th Mmrs." Apart from these, you can browse through new songs at the in-game store, preview them, and buy what you like for $ 0.99 each. The continuously growing library will ensure that you never get bored with the content, while two game modes (Practice and Studio) and a moderate level of difficulty provide a fair amount of variation and keep things challenging for even the most hardcore of players.

Finally, the developers have also decided to integrate Six-String with social gaming platform Plus+, allowing customers to earn achievements and points, compare scores over the online leaderboard, and even challenge other players to a music match. From the amount of features to the overall level of polish, it looks like rhythm app veterans have met their match. Needless to say, we highly recommend this game to fans of the genre!

Suggestions for improvement: For $ 4.99, we'd like to see more free tracks and maybe music bundles for purchase instead of individual songs at an additional $ 0.99 each. The game is also a little too difficult at times, even on Easy.